1. Technical Field
Example embodiments of the present invention generally relate to an image forming apparatus, a fixing unit, and/or an image forming method with an improved heating mechanism, e.g., for heating a fixing member to fix a toner image on a recording medium for example.
2. Description of Background Art
A background electrophotographic image forming apparatus, such as a copying machine, a printer, a facsimile machine, or a multifunction printer including copying, printing, and facsimile functions, generally forms an electrostatic latent image on a photoconductor according to image data. The electrostatic latent image is visualized with toner to form a toner image on the photoconductor. The toner image is transferred onto a sheet and the sheet having the toner image is conveyed to a fixing unit in which heat and pressure are applied to the sheet to fix the toner image on the sheet.
In such a fixing unit, a fixing member for applying heat to the sheet having the toner image needs to be heated to a fixing temperature in a shorter time period so as to enhance user-friendliness. Further, such fixing unit is desired to consume less power to save energy.
To cope with such needs, in an example background fixing unit, a fixing member is configured to have a thinner thickness (e.g., about 1 mm or less) to improve temperature response so as to be heated in a shorter time period. Power is supplied to a heater for heating the fixing member when an image forming operation starts while it is not supplied in a standby mode so as to save energy.
However, the fixing member having the thinner thickness has a small heat capacity and heat may be easily transferred to a sheet contacting the fixing member for fixing, resulting in an uneven temperature of the fixing member. To address this problem, another example background fixing unit is provided with a heat insulator for covering the fixing member to reduce heat radiation from the fixing member. However, the heat insulator may obstruct a quick heating of the fixing member.
To heat the fixing member in a shorter time period, yet another example background fixing unit is provided with an external heater disposed outside the fixing member and/or a heater disposed inside the fixing member to heat the fixing member. The external heater continuously contacts the fixing member or contacts and separates from the fixing member. However, the external heater contacting the fixing member may damage the fixing member.